I should of read your first post more clearly. If you system crashed while running Firefox, then I guess it could be possible your FIrefox is buggered up now. Have you tried re-installing Firefox? Or updating to the latest version?Firefox-2.0.0.7 is in the testing repo now.

segmentation fault (segfault) is a very general error, that's not very useful for troubleshooting or debugging. It means something went wrong trying to read from or write to memory. Usually, it has to do with a program trying to read past the end of data, or otherwise read memory that doesn't contain correct info.